1. Field of the Invention
The present invention relates to hot plug devices and methods of controlling power to a hot plug device.
2. Background of the Related Art
Many systems require the ability to hot plug a device into the system, and control the inrush current seen by the charging of input capacitance. In most technologies there is a balance between charging the capacitance as fast as you can so the FETs are not in a linear mode too long, and not tripping the over current of the regulator or any other upstream power supply. The main issue seen in industry is the fact there is an impedance that is lower than the over current trip point, but high enough to damage a FET if turned on into this impedance. This exposes hot plug mechanisms to cases where, if there is a failure on the rail and the impedance is a soft short, it can lead to severe power dissipation in the turn on FETs, and can lead to a double fault causing a severe burn in a server environment.
Another embodiment of the present invention provides a computer program product for controlling in rush current to a hot plug device. The computer program product comprises a computer readable storage medium having program instructions embodied therewith, where the program instructions are executable by a processor to cause the processor to perform a method. The method comprises providing a series of turn on pulses to the gates of a plurality of turn on FETs on a hot plug device coupled to a direct current power source, wherein each pulse causes the plurality of FETs to pass current from the direct current power source to a subsystem of the hot plug device, and wherein each pulse has a duration that ends before the impedance of the turn on FETs falls below a safe operating region. The method further comprises providing a steady turn on signal to the FETs in response to the output voltage from the FETs to a subsystem of the hot plug device exceeding a predetermined voltage threshold.